Mechanically-actuated Microfluidic Valve

ABSTRACT

A mechanically-actuated microfluidic valve. The valve comprises an inlet port; an outlet port; a thermal bend actuator; and a valve closure member cooperating with the actuator. Actuation of the thermal bend actuator causes movement of the closure member, thereby regulating a flow of fluid from the inlet port to the outlet port.

FIELD OF THE INVENTION

This invention relates to lab-on-a-chip (LOC) and microfluidicstechnology. It has been developed to provide fully integratedmicrofluidic systems (e.g. LOC devices), as well as microfluidic deviceswhich do not rely solely on soft lithographic fabrication processes.

CO-PENDING APPLICATIONS

The following applications have been filed by the Applicantsimultaneously with the present application:

LOC001US LOC002US LOC004US LOC005US LOC006US LOC007US LOC008US LOC009USLOC010US LOC011US LOC012US LOC013USThe disclosures of these co-pending applications are incorporated hereinby reference. The above applications have been identified by theirfiling docket number, which will be substituted with the correspondingapplication number, once assigned.

CROSS REFERENCES

The following patents or patent applications filed by the applicant orassignee of the present invention are hereby incorporated bycross-reference.

7344226 7328976 11/685084 11/685086 11/685090 11/740925 11/76344411/763443 11946840 11961712 12/017771 11/763440 11/763442 1211482612114827

BACKGROUND OF THE INVENTION

“Lab-on-a-chip” (LOC) is a term describing devices of only a few squaremillimeters or centimeters, which are able to perform a myriad of tasksnormally associated with a standard laboratory. LOC devices comprisemicrofluidic channels, which and are capable of handling very smallfluid volumes in the nanoliter or picoliter range. The applicability ofLOC devices for chemical and biological analysis has fuelled research inthis field, especially if LOC devices can be fabricated cheaply enoughto provide disposable biological analysis tools. For example, one of thegoals of LOC technology is to provide real-time DNA detection devices,which can be used once and then disposed of.

Fabrication of LOC devices evolved from standard MEMS technology,whereby well-established photolithographic techniques are used forfabricating devices on silicon wafers. Fluidic control is crucial formost LOC devices. Accordingly, LOC devices typically comprise an arrayof individually controllable microfluidics devices, such as valves andpumps. Although LOC devices originally evolved from silicon-based MEMStechnology, more recently there has been general shift towards softlithography, which employs elastomeric materials. Elastomers are farmore suitable than silicon for forming effective valve seals. Thus,polydimethylsiloxane (PDMS) has now become the material of choice forfabricating microfluidics devices in LOC chips. A PDMS microfluidicsplatform is typically fabricated using soft lithography and then mountedon a glass substrate.

One of the most common types of valve employed in LOC devices is the‘Quake’ valve, as described in U.S. Pat. No. 7,258,774, the contents ofwhich is incorporated herein by reference. The ‘Quake’ valve usesfluidic pressure (e.g. pneumatic pressure or hydraulic pressure) in acontrol channel to collapse a PDMS wall of an adjacent fluid flowchannel, in the manner of a conventional pneumatic pinch valve.Referring briefly to FIGS. 1A-C, the Quake valve comprises a fluid flowchannel 1 and control channel 2, which extends transversely across thefluid flow channel 1. A membrane 3 separates the channels 1 and 2. Thechannels 1 and 2 are defined in a flexible elastomeric substrate, suchas PDMS, using soft lithography so as to provide a microfluidicstructure 4. The microfluidic structure 4 is bonded to a planarsubstrate 5, such as a glass slide.

As shown in FIG. 1B, the fluid flow channel 1 is “open”. In FIG. 1C,pressurization of the control channel 2 (either by gas or liquidintroduced therein by an external pump) causes the membrane 3 to deflectdownwards, thereby pinching the fluid flow channel 1 and controlling aflow of fluid through the channel 1. Accordingly, by varying thepressure in control channel 2, a linearly actuable valving system isprovided such that fluid flow channel 1 can be opened or closed bymoving membrane 3 as desired. (For illustration purposes only, the fluidflow channel 1 in FIG. 1C is shown in a “mostly closed” position, ratherthan a “fully closed” position).

A plurality of Quake valves may cooperate to provide a peristaltic pump.Hence, the ‘Quake’ valving system has been used to create thousands ofvalves and pumps in one LOC device. As foreshadowed above, the number ofpotential chemical and biological applications of such devices is vast,ranging from fuel cells to DNA sequencers.

However, current microfluidics devices, such as those described in U.S.Pat. No. 7,258,774, suffer from a number of problems. In particular,these prior art microfluidics devices must be plugged into externalcontrol systems, air/vacuum systems and/or pumping systems in order tofunction. Whilst the microfluidics platform formed by soft lithographymay be small and cheap to manufacture, the external support systemsrequired to drive the microfluidics devices means that the resultingμTAS device is relatively expensive and much larger than the actualmicrofluidics platform. Hence, current technology is still unable toprovide fully integrated, disposable LOC or μTAS devices. It would bedesirable to provide a fully integrated LOC device, which does notrequire a plethora of external support systems to drive the device.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a peristalticmicrofluidic pump comprising:

-   -   a pumping chamber positioned between an inlet and an outlet;    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall; and    -   a plurality of thermal bend actuators, each actuator being        associated with a respective finger such that actuation of said        thermal bend actuator causes movement of said respective finger        into said pumping chamber,        wherein said pump is configured to provide a peristaltic pumping        action in said pumping chamber via movement of said fingers.

Optionally, the pumping chamber is elongate, and said fingers arearranged in a row along a longitudinal wall of said pumping chamber.

Optionally, each finger extends transversely across said chamber.

Optionally, said fingers are arranged in opposed pairs of fingers, eachfinger in an opposed pair pointing towards a central longitudinal axisof said pumping chamber.

Optionally, each finger comprises said thermal bend actuator.

Optionally, said pumping chamber comprises a roof spaced apart from asubstrate, and sidewalls extending between said roof and a floor definedby said substrate.

Optionally, said fingers are positioned in said roof.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of each finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling each actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said substrate comprises control circuitry for controllingeach actuator.

Optionally, said substrate is a silicon substrate having said controlcircuitry contained in at least one CMOS layer thereof.

Optionally, said wall is covered with a polymeric layer, said polymericlayer providing a mechanical seal between each finger and said wall.

Optionally, said polymeric layer is comprised of polydimethylsiloxane(PDMS).

Optionally, said inlet is defined in said substrate.

In a further aspect there is provided a microfluidic system comprisingthe microfluidic pump comprising:

-   -   a pumping chamber positioned between an inlet and an outlet;    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall; and    -   a plurality of thermal bend actuators, each actuator being        associated with a respective finger such that actuation of said        thermal bend actuator causes movement of said respective finger        into said pumping chamber,        wherein said pump is configured to provide a peristaltic pumping        action in said pumping chamber via movement of said fingers.

In another aspect there is provided a microfluidic system comprising themicrofluidic pump comprising:

-   -   a pumping chamber positioned between an inlet and an outlet;    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall; and    -   a plurality of thermal bend actuators, each actuator being        associated with a respective finger such that actuation of said        thermal bend actuator causes movement of said respective finger        into said pumping chamber,        wherein said pump is configured to provide a peristaltic pumping        action in said pumping chamber via movement of said fingers,        which is a LOC device or a Micro Total Analysis System.

In a second aspect the present invention provides a MEMS integratedcircuit comprising one or more peristaltic microfluidic pumps andcontrol circuitry for said one or more pumps, each pump comprising:

-   -   a pumping chamber positioned between an inlet and an outlet;    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall; and    -   a plurality of thermal bend actuators, each actuator being        associated with a respective finger such that actuation of said        thermal bend actuator causes movement of said respective finger        into said pumping chamber,        wherein said control circuitry controls actuation of said        plurality of actuators, and said control circuitry is configured        to provide a peristaltic pumping action in each pumping chamber        via peristaltic movement of said fingers.

Optionally, the pumping chamber is elongate, and said fingers arearranged in a row along a longitudinal wall of said pumping chamber.

Optionally, each finger extends transversely across said chamber.

Optionally, said fingers are arranged in opposed pairs of fingers, eachfinger in an opposed pair pointing towards a central longitudinal axisof said pumping chamber.

Optionally, each finger comprises said thermal bend actuator.

Optionally, said pumping chamber comprises a roof spaced apart from asubstrate, and sidewalls extending between said roof and a floor definedby said substrate.

Optionally, said fingers are positioned in said roof.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of each finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to saidcontrol circuitry.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said substrate is a silicon substrate having said controlcircuitry contained in at least one CMOS layer thereof.

Optionally, said wall is covered with a polymeric layer, said polymericlayer providing a mechanical seal between each finger and said wall.

Optionally, said polymeric layer is comprised of polydimethylsiloxane(PDMS).

Optionally, said polymeric layer defines an exterior surface of saidMEMS integrated circuit.

Optionally, said outlet is defined in said exterior surface.

Optionally, said inlet is defined in said substrate.

In another aspect there is provided a microfluidic system comprising theMEMS integrated circuit comprising one or more peristaltic microfluidicpumps and control circuitry for said one or more pumps, each pumpcomprising:

-   -   a pumping chamber positioned between an inlet and an outlet;    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall; and    -   a plurality of thermal bend actuators, each actuator being        associated with a respective finger such that actuation of said        thermal bend actuator causes movement of said respective finger        into said pumping chamber,        wherein said control circuitry controls actuation of said        plurality of actuators, and said control circuitry is configured        to provide a peristaltic pumping action in each pumping chamber        via peristaltic movement of said fingers.

In a third aspect the present invention provides a mechanically-actuatedmicrofluidic valve comprising:

-   -   an inlet port;    -   an outlet port;    -   a thermal bend actuator; and    -   a valve closure member cooperating with said actuator, such that        actuation of said thermal bend actuator causes movement of said        closure member, thereby regulating a flow of fluid from said        inlet port to said outlet port.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, at least said actuator is defined in a MEMS layer of asilicon substrate.

Optionally, said substrate comprises control circuitry for controllingsaid actuator, said control circuitry being contained in at least oneCMOS layer of said substrate.

Optionally, said inlet port and said outlet port are defined in a MEMSlayer of a silicon substrate.

Optionally, said inlet port and said outlet port are defined inpolymeric microfluidics platform.

Optionally, said closure member is comprised of a compliant material forsealing engagement with a sealing surface of said valve.

Optionally, said closure member is comprised of an elastomer.

Optionally, said closure member is comprised of polydimethylsiloxane(PDMS).

Optionally, said closure member is fused or bonded to said thermal bendactuator.

Optionally, said actuation causes open or closing of said valve.

Optionally, said actuation causes partial opening or partial closing ofsaid valve.

In a fourth aspect the present invention provides a microfluidic systemcomprising a MEMS integrated circuit bonded to a polymeric microfluidicsplatform, said system comprising one or more microfluidic devices,wherein at least one of said microfluidic devices comprises a MEMSactuator positioned in a MEMS layer of said integrated circuit.

Optionally, said microfluidic devices are selected from the groupcomprising: microfluidic valves and microfluidic pumps.

Optionally, all of said microfluidic devices comprise a MEMS actuatorpositioned in said MEMS layer.

Optionally, said MEMS layer further comprises a microheater for heatinga fluid in a microfluidic channel.

Optionally, said MEMS integrated circuit comprises a silicon substrateand said MEMS layer is formed on said substrate.

Optionally, said MEMS layer is covered with a polymeric layer.

Optionally, said polymeric layer defines a bonding surface of said MEMSintegrated circuit.

Optionally, said polymeric layer is comprised of photopatternable PDMS.

Optionally, said microfluidics platform comprises a polymeric bodyhaving one or more microfluidic channels defined therein.

Optionally, said polymeric body is comprised of PDMS.

Optionally, at least one of said microfluidic channels is in fluidcommunication with said at least one microfluidic device.

Optionally, said MEMS integrated circuit comprises control circuitry forcontrolling said actuator, said control circuitry being contained in atleast one CMOS layer of said substrate.

Optionally, said MEMS actuator is a thermal bend actuator.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

In a further aspect there is provided a microfluidic system comprising aMEMS integrated circuit bonded to a polymeric microfluidics platform,said system comprising one or more microfluidic devices, wherein atleast one of said microfluidic devices comprises a MEMS actuatorpositioned in a MEMS layer of said integrated circuit,

which is a LOC device or a Micro Total Analysis System (μTAS).

In a fifth aspect the present invention provides a microfluidic systemcomprising an integrated circuit having a bonding surface bonded to apolymeric microfluidics platform, said microfluidic system comprisingone or more microfluidics devices controlled by control circuitry insaid integrated circuit,

wherein at least one of said microfluidic devices comprises a MEMSactuator positioned in a MEMS layer of said integrated circuit, saidMEMS layer being covered with a polymeric layer which defines saidbonding surface of said integrated circuit.

Optionally, said microfluidic devices are selected from the groupcomprising: microfluidic valves and microfluidic pumps.

Optionally, said microfluidic devices are positioned in any one of:

-   -   said integrated circuit;    -   said microfluidics platform; and    -   an interface between said integrated circuit and said        microfluidics platform.

Optionally, said integrated circuit comprises a silicon substrate havingat least one CMOS layer, and said control circuitry is contained in saidat least one CMOS layer.

Optionally, said integrated circuit comprises a silicon substrate andsaid MEMS layer is formed on said substrate.

Optionally, said polymeric layer is comprised of photopatternable PDMS.

Optionally, said microfluidics platform comprises a polymeric bodyhaving one or more microfluidic channels defined therein.

Optionally, said polymeric body is comprised of PDMS.

Optionally, at least one of said microfluidic channels is in fluidcommunication with at least one said microfluidic devices.

Optionally, said MEMS actuator is a thermal bend actuator.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to saidcontrol circuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said integrated circuit is in fluidic communication and/ormechanical communication with said polymeric microfluidics platform.

In another aspect there is provided a microfluidic system comprising anintegrated circuit having a bonding surface bonded to a polymericmicrofluidics platform, said microfluidic system comprising one or moremicrofluidics devices controlled by control circuitry in said integratedcircuit,

wherein at least one of said microfluidic devices comprises a MEMSactuator positioned in a MEMS layer of said integrated circuit, saidMEMS layer being covered with a polymeric layer which defines saidbonding surface of said integrated circuit, which is a LOC device or aMicro Total Analysis System (μTAS).

In a sixth aspect the present invention provides a microfluidic systemcomprising a MEMS integrated circuit, said MEMS integrated circuitcomprising:

-   -   a silicon substrate having one or more microfluidic channels        defined therein;    -   at least one layer of control circuitry for controlling one or        more microfluidic devices;    -   a MEMS layer comprising said one or more microfluidic devices;        and    -   a polymeric layer covering said MEMS layer,        wherein at least part of said polymeric layer provides a seal        for at least one of said microfluidic devices.

Optionally, said MEMS integrated circuit contains all the microfluidicdevices and control circuitry required for operation of saidmicrofluidic system.

Optionally, said microfluidic devices are selected from the groupcomprising: microfluidic valves and microfluidic pumps.

Optionally, said control circuitry is contained in at least one CMOSlayer.

Optionally, said polymeric layer is comprised of photopatternable PDMS.

Optionally, said polymeric layer defines an exterior surface of saidMEMS integrated circuit.

Optionally, MEMS integrated circuit is mounted on a passive substratevia said polymeric layer.

Optionally, said at least one microfluidic device comprises a MEMSactuator.

Optionally, said MEMS actuator is a thermal bend actuator.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to saidcontrol circuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said microfluidic device is a microfluidic valve comprisinga sealing surface positioned between an inlet port and an outlet ports,and wherein said at least part of said polymeric layer is configured forsealing engagement with said sealing surface.

Optionally, said sealing engagement regulates fluid flow from said inletport to said outlet port.

Optionally, said microfluidic device is a microfluidic peristaltic pumpcomprising:

-   -   a pumping chamber positioned between an inlet and an outlet; and    -   a plurality of moveable fingers positioned in a wall of said        pumping chamber, said fingers being arranged in a row along said        wall and configured to provide a peristaltic pumping action via        movement of said fingers,        wherein said at least part of said polymeric layer provides a        mechanical seal between each moveable finger and said wall.

In a further aspect there is provided a microfluidic system comprising aMEMS integrated circuit, said MEMS integrated circuit comprising:

-   -   a silicon substrate having one or more microfluidic channels        defined therein;    -   at least one layer of control circuitry for controlling one or        more microfluidic devices;    -   a MEMS layer comprising said one or more microfluidic devices;        and    -   a polymeric layer covering said MEMS layer,        wherein at least part of said polymeric layer provides a seal        for at least one of said microfluidic devices,    -   which is a LOC device Micro Total Analysis System (μTAS).

In a seventh aspect the present invention provides a microfluidic valvecomprising:

-   -   an inlet port;    -   an outlet port;    -   a weir positioned between said inlet and outlet ports, said weir        having a sealing surface;    -   a diaphragm membrane for sealing engagement with said sealing        surface; and    -   at least one thermal bend actuator for moving said diaphragm        membrane between a closed position in which said membrane is        sealingly engaged with said sealing surface and an open position        in which said membrane is disengaged from said sealing surface.

Optionally, in said open position, a connecting channel is definedbetween said diaphragm membrane and said sealing surface, saidconnecting channel providing fluidic communication between said inletand outlet ports.

Optionally, said open position includes a fully open position and apartially open position.

Optionally, said diaphragm membrane is fused or bonded to at least onemoveable finger, said actuator causing movement of said finger.

Optionally, said at least one finger comprises said thermal bendactuator.

Optionally, the microfluidic valve according to the present inventioncomprising a pair of opposed fingers, each of said fingers pointingtowards said weir, wherein said diaphragm membrane bridges between saidopposed fingers.

Optionally, said valve is formed on a substrate, said diaphragm membraneand said fingers being spaced apart from said substrate, and said weirextending from said substrate towards said diaphragm membrane.

Optionally, said weir is positioned centrally between said opposedfingers.

Optionally, each of said fingers comprises a respective thermal bendactuator.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of each finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling each actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said substrate comprises control circuitry for controllingsaid at least one actuator.

Optionally, said substrate is a silicon substrate having said controlcircuitry contained in at least one CMOS layer thereof.

Optionally, said diaphragm membrane is defined by at least part of apolymeric layer.

Optionally, said polymeric layer is comprised of polydimethylsiloxane(PDMS).

Optionally, a plurality of the microfluidic valves according to thepresent invention are arranged in series for use in peristaltic pump.

In an eighth aspect the present invention provides a MEMS integratedcircuit comprising one or more microfluidic diaphragm valves and controlcircuitry for said one or more valves, each valve comprising:

-   -   an inlet port;    -   an outlet port;    -   a weir positioned between said inlet and outlet ports, said weir        having a sealing surface;    -   a diaphragm membrane for sealing engagement with said sealing        surface; and    -   at least one thermal bend actuator for moving said diaphragm        membrane between a closed position in which said membrane is        sealingly engaged with said sealing surface and an open position        in which said membrane is disengaged from said sealing surface,        wherein said control circuitry is configured to control        actuation of said at least one actuator so as to control opening        and closing of said valve.

Optionally, in said open position, a connecting channel is definedbetween said diaphragm membrane and said sealing surface, saidconnecting channel providing fluidic communication between said inletand outlet ports.

Optionally, said open position includes a fully open position and apartially open position, a degree of opening being controlled by saidcontrol circuitry.

Optionally, said diaphragm membrane is fused or bonded to at least onemoveable finger, said actuator causing movement of said finger.

Optionally, said at least one finger comprises said thermal bendactuator.

Optionally, the MEMS integrated circuit according to the presentinvention comprising a pair of opposed fingers, each of said fingerspointing towards said weir, wherein said diaphragm membrane bridgesbetween said opposed fingers.

Optionally, said valve is formed on a substrate, said diaphragm membraneand said fingers being spaced apart from said substrate, and said weirextending from said substrate towards said diaphragm membrane.

Optionally, said weir is positioned centrally between said opposedfingers.

Optionally, each of said fingers comprises a respective thermal bendactuator.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of each finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling each actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said substrate is a silicon substrate having said controlcircuitry contained in at least one CMOS layer thereof.

Optionally, said diaphragm membrane is defined by at least part of apolymeric layer.

Optionally, said polymeric layer is comprised of polydimethylsiloxane(PDMS).

Optionally, said polymeric layer defines an exterior surface of saidMEMS integrated circuit.

Optionally, a plurality of said valves are arranged in series and saidcontrol circuitry is configured to control actuation of each actuator soas to provide a peristaltic pumping action.

In a ninth aspect the present invention provides a microfluidic pinchvalve comprising:

-   -   a microfluidic channel defined in a compliant body;    -   a valve sleeve defined by a section of said microfluidic        channel, said valve sleeve having a membrane wall defining at        least part of an outer surface of said body;    -   a compression member for pinching said membrane wall against an        opposed wall of said valve sleeve; and    -   a thermal bend actuator for moving said compression member        between a closed position in which said membrane wall is        sealingly pinched against said opposed wall, and an open        position in which said membrane wall is disengaged from said        opposed wall.

Optionally, said open position includes a fully open position and apartially open position.

Optionally, a moveable finger is engaged with said compression member,said finger being configured to urge said compression member betweensaid open and closed positions via movement of said actuator.

Optionally, said compression member is sandwiched between said fingerand said membrane wall.

Optionally, said compression member protrudes from said membrane wall.

Optionally, said compression member is biased towards said closedposition when said thermal bend actuator is in a quiescent state.

Optionally, a MEMS integrated circuit is bonded to said outer surface ofsaid body, said moveable finger being contained in a MEMS layer of saidintegrated circuit.

Optionally, said MEMS integrated circuit comprises a bonding surfacedefined by a polymeric layer, said bonding surface being bonded to saidouter surface of said body.

Optionally, said polymeric layer covers said MEMS layer.

Optionally, said polymeric layer and/or said compliant body arecomprised of PDMS.

Optionally, actuation of said actuator causes said finger to move awayfrom said body, thereby opening said valve; and

-   -   deactuation of said actuator causes said finger to move towards        said body, thereby closing said valve.

Optionally, said moveable finger comprises said thermal bend actuator.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of said finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling each actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys; and said passive beam is comprised of amaterial selected from the group comprising: silicon oxide, siliconnitride and silicon oxynitride.

Optionally, said MEMS integrated circuit comprises a silicon substratehaving control circuitry contained in at least one CMOS layer.

Optionally, there is provided a microfluidic system comprising themicrofluidic valve according to the present invention.

Optionally, the microfluidic system according to the present inventioncomprising a plurality of said valves arranged in series.

In a tenth aspect the present invention provides a microfluidic systemcomprising:

(A) a microfluidics platform comprising:

-   -   a compliant body having a microfluidic channel defined therein;    -   a valve sleeve defined by a section of said microfluidic        channel, said valve sleeve having a membrane wall defining at        least part of an outer surface of said body; and    -   a compression member for pinching said membrane wall against an        opposed wall of said valve sleeve; and        (B) a MEMS integrated circuit bonded to said outer surface of        said body, said MEMS integrated circuit comprising:    -   a moveable finger engaged with said compression member, said        finger being configured to urge said compression member between        a closed position in which said membrane wall is sealingly        pinched against said opposed wall, and an open position in which        said membrane wall is disengaged from said opposed wall;    -   a thermal bend actuator associated with said finger, said        actuator configured for controlling movement of said finger; and    -   control circuitry for controlling actuation of said actuator so        as to control opening and closing of said valve sleeve.

Optionally, said open position includes a fully open position and apartially open position.

Optionally, said compression member is sandwiched between said fingerand said membrane wall.

Optionally, said compression member protrudes from said membrane wall.

Optionally, said compression member is part of said membrane wall.

Optionally, said compression member is biased towards said closedposition when said thermal bend actuator is in a quiescent state.

Optionally, said MEMS integrated circuit comprises a bonding surfacedefined by a polymeric layer, said bonding surface being bonded to saidouter surface of said body.

Optionally, said polymeric layer covers a MEMS layer containing saidmoveable finger.

Optionally, said polymeric layer and/or said compliant body arecomprised of PDMS.

Optionally, actuation of said actuator causes said finger to move awayfrom said body, thereby opening said valve sleeve; and

-   -   deactuation of said actuator causes said finger to move towards        said body, thereby closing said valve sleeve.

Optionally, said moveable finger comprises said thermal bend actuator.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of said finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to saidcontrol circuitry.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys.

Optionally, said passive beam is comprised of a material selected fromthe group comprising: silicon oxide, silicon nitride and siliconoxynitride.

Optionally, said MEMS integrated circuit comprises a silicon substratehaving said control circuitry contained in at least one CMOS layer.

In an eleventh aspect the present invention provides a microfluidicsystem comprising:

(A) a microfluidics platform comprising:

-   -   a compliant body having a microfluidic channel defined therein;    -   an elongate chamber defined by a section of said microfluidic        channel, said chamber having a membrane wall defining at least        part of an outer surface of said body; and    -   a plurality of compression members spaced apart along said        membrane wall, each compression member being configured for        pinching a respective part of said membrane wall against an        opposed wall of said chamber; and

(B) a MEMS integrated circuit bonded to said outer surface of said body,said MEMS integrated circuit comprising:

-   -   a plurality of moveable fingers, each finger engaged with a        respective compression member, each finger being configured to        urge said respective compression member between a closed        position in which said respective part of said membrane wall is        sealingly pinched against said opposed wall, and an open        position in which said respective part of said membrane wall is        disengaged from said opposed wall;    -   a plurality of thermal bend actuators, each associated with a        respective finger for controlling movement of said respective        finger, and    -   control circuitry for controlling actuation of said actuators.

Optionally, said control circuitry is configured to provide one or moreof:

-   -   (i) a peristaltic pumping action in said chamber via peristaltic        movement of said fingers;    -   (ii) a mixing action in said chamber via movement of said        fingers;    -   (iii) a concerted valving action in said chamber.

Optionally, said mixing action generates a turbulent flow of fluidthrough said chamber.

Optionally, said concerted valving action concertedly moves all saidcompression members into either an open position or a closed position.

Optionally, said control circuitry is configured to provideinterchangeably two or more of said peristaltic pumping action, saidmixing action and said concerted valving action.

Optionally, each compression member is sandwiched between its respectivefinger and said membrane wall.

Optionally, each compression member protrudes from said membrane wall.

Optionally, each compression member is part of said membrane wall.

Optionally, each compression member is biased towards said closedposition when said thermal bend actuator is in a quiescent state.

Optionally, said MEMS integrated circuit comprises a bonding surfacedefined by a polymeric layer, said bonding surface being bonded to saidouter surface of said body.

Optionally, said polymeric layer covers a MEMS layer containing saidmoveable finger.

Optionally, said polymeric layer and/or said compliant body arecomprised of PDMS.

Optionally, actuation of each actuator causes its respective finger tomove away from said body, thereby disengaging a respective part of saidmembrane wall from said opposed wall; and

-   -   deactuation of each actuator causes said respective finger to        move towards said body, thereby sealingly pinching a respective        part of said membrane wall against said opposed wall.

Optionally, each moveable finger comprises said thermal bend actuator.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, an extent of each finger is defined by said passive beam.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to saidcontrol circuitry.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys; and said passive beam is comprised of amaterial selected from the group comprising: silicon oxide, siliconnitride and silicon oxynitride.

Optionally, said MEMS integrated circuit comprises a silicon substratehaving said control circuitry contained in at least one CMOS layer.

In a twelfth aspect the present invention provides a microfluidic systemcomprising a MEMS integrated circuit bonded to a microfluidics platform,said microfluidics platform comprising a polymeric body having at leastone microfluidic channel defined therein, and said MEMS integratedcircuit comprising at least one thermal bend actuator, wherein saidmicrofluidic system is configured such that movement of said at leastone actuator causes closure of said channel.

Optionally, said at least one thermal bend actuator is associated with arespective moveable finger such that actuation of said thermal bendactuator causes movement of said respective finger.

Optionally, said finger is engaged with a wall of said microfluidicchannel.

Optionally a microfluidic system according to the present inventionwhich is configured such that movement of said finger towards saidmicrofluidics platform causes closure of said channel by pinching saidwall against an opposed wall.

Optionally, said movement is provided by deactuation of said thermalbend actuator.

Optionally a microfluidic system according to the present inventioncomprising a plurality of moveable fingers configured as a linearperistaltic pump.

Optionally, said pump is in fluidic communication with a control channeldefined in said polymeric body, said control channel cooperating withsaid microfluidic channel such that pressurizing said control channelwith a control fluid causes pinching closure of said microfluidicchannel.

Optionally, said control fluid is a gas providing pneumatic control, ora liquid providing hydraulic control.

Optionally, said at least one thermal bend actuator is positioned in aMEMS layer of said MEMS integrated circuit.

Optionally, said MEMS integrated circuit comprises a silicon substrateand said MEMS layer is formed on said substrate.

Optionally, said MEMS integrated circuit comprises control circuitry forcontrolling said at least one thermal bend actuator, said controlcircuitry being contained in at least one CMOS layer of said substrate.

Optionally, said MEMS layer is covered with a polymeric layer.

Optionally, said polymeric layer defines a bonding surface of said MEMSintegrated circuit.

Optionally, said polymeric layer is comprised of photopatternable PDMS.

Optionally, said polymeric body is comprised of PDMS.

Optionally, said thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys; and said passive beam is comprised of amaterial selected from the group comprising: silicon oxide, siliconnitride and silicon oxynitride.

Optionally, a microfluidic system according the present invention whichis a LOC device or a Micro Total Analysis System (μTAS).

In a thirteenth aspect the present invention provides a microfluidicsystem comprising a pneumatic or an hydraulic pinch valve, said pinchvalve comprising:

-   -   a microfluidic channel defined in a compliant body;    -   an inflatable control channel cooperating with a valve section        of said microfluidic channel such that pneumatic or hydraulic        pressurization of said control channel causes inflation of said        control channel and pinching closure of said valve section,        wherein said microfluidic system comprises an on-chip MEMS pump        in fluidic communication with said control channel for        pressurizing said control channel.

Optionally, said valve section comprises resiliently collapsible walls.

Optionally, a wall of said control channel is engaged with a wall ofsaid valve section.

Optionally, shutting off said pump releases a pressure in said controlchannel, thereby opening said valve section.

Optionally, the microfluidic system according to the present inventioncomprises on-chip control circuitry for controlling said pump, andthereby controlling closure of said valve section.

Optionally, the microfluidic system according to the present inventioncomprises a MEMS integrated circuit bonded to a microfluidics platform,said microfluidics platform comprising a polymeric body having saidmicrofluidic channel and said control channel defined therein, and saidMEMS integrated circuit comprising said MEMS pump.

Optionally, said MEMS pump comprises a plurality of moveable fingersconfigured as a linear peristaltic pump, each of said fingers beingassociated with a respective thermal bend actuator for moving arespective finger.

Optionally, each finger comprises a respective thermal bend actuator.

Optionally, said MEMS pump is positioned in a MEMS layer of said MEMSintegrated circuit.

Optionally, said MEMS integrated circuit comprises a silicon substrateand said MEMS layer is formed on said substrate.

Optionally, said MEMS integrated circuit comprises control circuitry forcontrolling said thermal bend actuators, said control circuitry beingcontained in at least one CMOS layer of said substrate.

Optionally, said MEMS layer is covered with a polymeric layer.

Optionally, said polymeric layer defines a bonding surface of said MEMSintegrated circuit.

Optionally, said polymeric layer is comprised of photopatternable PDMS.

Optionally, said compliant body is comprised of PDMS.

Optionally, each thermal bend actuator comprises:

-   -   an active beam comprised of a thermoelastic material; and    -   a passive beam mechanically cooperating with said active beam,        such that when a current is passed through the active beam, the        active beam heats and expands relative to the passive beam,        resulting in bending of the actuator.

Optionally, said active beam is fused to said passive beam.

Optionally, said passive beam defines an extent of each finger.

Optionally, said active beam defines a bent current path extendingbetween a pair of electrodes, said electrodes being connected to controlcircuitry for controlling said actuator.

Optionally, said thermoelastic material is selected from the groupcomprising: titanium nitride, titanium aluminium nitride andvanadium-aluminium alloys; and said passive beam is comprised of amaterial selected from the group comprising: silicon oxide, siliconnitride and silicon oxynitride.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying drawings, in which:

FIGS. 1A-C show a prior art valving system;

FIG. 2 shows a partially-fabricated thermal bend-actuated inkjet nozzleassembly;

FIG. 3 is a cutaway perspective of a completed inkjet nozzle assembly;

FIG. 4 is a perspective of a MEMS microfluidic pump with a polymericsealing layer removed to reveal MEMS devices;

FIG. 5 is a cutaway perspective of the pump shown in FIG. 4 whichincludes the polymeric sealing layer;

FIG. 6 is a plan view of an alternative MEMS microfluidic pump;

FIG. 7 shows schematically a microfluidics platform and a MEMSintegrated circuit prior to bonding;

FIG. 8 shows schematically an integrated LOC device comprising a bondedmicrofluidics platform and MEMS integrated circuit;

FIG. 9 shows schematically a microfluidic pinch valve fabricated bybonding a microfluidics platform with a MEMS integrated circuit;

FIG. 10 shows the microfluidic pinch valve of FIG. 9 in an openposition;

FIG. 11 shows a multifunctional device comprising a plurality ofmicrofluidic pinch valves, as shown in FIG. 10, arranged in series;

FIG. 12 shows a microfluidic diaphragm valve in an open position; and

FIG. 13 shows the microfluidic diaphragm valve of FIG. 12 in a closedposition.

DETAILED DESCRIPTION OF THE INVENTION

For the avoidance of doubt, the term “microfluidics”, as used herein,has its usual meaning in the art. Typically microfluidic systems orstructures are constructed on a micron scale and comprise at least onemicrofluidic channel having a width of less than about 1000 microns. Themicrofluidic channels usually have a width in the range of 1-800microns, 1-500 microns, 1-300 microns 2-250 microns, 3-150 microns or 5to 100 microns. Microfluidic systems and devices are typically capableof handling fluidic quantities of less than about 1000 nanoliters, lessthan 100 nanoliters, less than 10 nanoliters, less than 1 nanoliter,less than 100 picoliters or less than 10 picoliters.

As used herein, the term “microfluidic system” refers to a single,integrated unit which is usually in the form of a ‘chip’ (in the sensethat it has similar dimensions to a typical microchip). A microfluidic‘chip’ typically has width and/or length dimensions of less than about 5cm, less than about 4 cm, less than about 3 cm, less than about 2 cm, orless than about 1 cm. The chip typically has a thickness of less thanabout 5 mm, less than about 2 mm or less than about 1 mm. The chip maybe mounted on a passive substrate, such as a glass slide, to provide itwith structural rigidity and robustness.

A microfluidic system typically comprises one or more microfluidicchannels and one or more microfluidic devices (e.g. micropumps,microvalves etc). Moreover, the microfluidic systems described hereintypically contain all the requisite support systems (e.g. controlcircuitry) for driving microfluidic devices in the system.

As used herein, the term “microfluidics platform” refers to a platformof, for example, microfluidic channels, microfluidic chambers and/ormicrofluidic devices, which traditionally requires external supportsystems for operation (e.g. off-chip pumps, off-chip control circuitryetc.). Microfluidics platforms typically have a polymeric body formed bysoft lithography. As will become apparent, a microfluidics platform mayform part of a bonded microfluidic system according to the presentinvention. Bonded microfluidic systems according to the presentinvention generally comprise an integrated circuit bonded to amicrofluidics platform via an interfacial bond. Typically, a bondedmicrofluidic system has fluidic communication and/or mechanicalcommunication between the integrated circuit and the microfluidicsplatform “Lab-on-a-Chip” or LOC devices are examples of microfluidicsystems. Generally, LOC is a term used to indicate the scaling of singleor multiple laboratory processes down to chip-format. A LOC devicetypically comprises a plurality of microfluidic channels, microfluidicchambers and microfluidic devices (e.g. micropumps, microvalves etc.)

A “Micro Total Analysis System” (μTAS) is an example of a LOC devicespecifically configured to perform a sequence of lab processes whichenable chemical or biological analysis.

Any of the microfluidic systems according to the present invention maybe a LOC device or a μTAS. The person skilled in the art will be capableof designing specific architectures for LOC devices (or, indeed, anymicrofluidic system) tailored to a particular application, utilizing thepresent teaching. Some typical applications of microfluidic systems areenzymatic analysis (e.g. glucose and lactate assays), DNA analysis (e.g.polymerase chain reaction and high-throughput sequencing), proteomics,disease diagnosis, analysis of air/water samples for toxins/pathogens,fuel cells, micromixers etc. The number of traditional laboratoryoperations that may be performed in a LOC device is virtually limitless,and the present invention is not limited to any particular applicationof microfluidics technology.

Thermal Bend Actuation in Inkjet Nozzle Assemblies

Hitherto, the present Applicant has described a plethora of thermalbend-actuated inkjet nozzle assemblies suitable for forming pagewidthprintheads. Some elements of these inkjet nozzles are relevant to themicrofluidic systems and devices described and claimed herein.Accordingly, a brief description of an inkjet nozzle assembly nowfollows.

Typically, inkjet nozzle assemblies are constructed on a surface of aCMOS silicon substrate. The CMOS layer of the substrate provides all thenecessary logic and drive circuitry (i.e. “control circuitry”) foractuating each nozzle of the printhead.

FIGS. 2 and 3 show one such nozzle assembly 100 at two different stagesof fabrication, as described in the Applicant's earlier U.S. applicationSer. No. 11/763,440 filed on Jun. 15, 2007, the contents of which isincorporated herein by reference.

FIG. 1 shows the nozzle assembly partially formed so as to illustratethe features of bend actuator. Thus, referring to FIG. 1, there is shownthe nozzle assembly 100 formed on a CMOS silicon substrate 102. A nozzlechamber is defined by a roof 104 spaced apart from the substrate 102 andsidewalls 106 extending from the roof to the substrate 102. The roof 104is comprised of a moving portion 108 and a stationary portion 110 with agap 109 defined therebetween. A nozzle opening 112 is defined in themoving portion 108 for ejection of ink.

The moving portion 108 comprises a thermal bend actuator having a pairof cantilever beams in the form of an upper active beam 114 fused to alower passive beam 116. The lower passive beam 116 defines the extent ofthe moving portion 108 of the roof. The upper active beam 114 comprisesa pair of arms 114A and 114B which extend longitudinally from respectiveelectrode contacts 118A and 118B. The arms 114A and 114B are connectedat their distal ends by a connecting member 115. The connecting member115 comprises a titanium conductive pad 117, which facilitateselectrical conduction around this join region. Hence, the active beam114 defines a bent or tortuous conduction path between the electrodecontacts 118A and 118B.

The electrode contacts 118A and 118B are positioned adjacent each otherat one end of the nozzle assembly and are connected via respectiveconnector posts 119 to a metal CMOS layer 120 of the substrate 102. TheCMOS layer 120 contains the requisite drive circuitry for actuation ofthe bend actuator.

The passive beam 116 is typically comprised of anyelectrically/thermally-insulating material, such as silicon dioxide,silicon nitride etc. The thermoelastic active beam 114 may be comprisedof any suitable thermoelastic material, such as titanium nitride,titanium aluminium nitride and aluminium alloys. As explained in theApplicant's copending U.S. application Ser. No. 11/607,976 filed on 4Dec. 2006 (Attorney Docket No. IJ70US), vanadium-aluminium alloys are apreferred material, because they combine the advantageous properties ofhigh thermal expansion, low density and high Young's modulus.

Referring to FIG. 3, there is shown a completed nozzle assembly at asubsequent stage of fabrication. The nozzle assembly 100 of FIG. 2 has anozzle chamber 122 and an ink inlet 124 for supply of ink to the nozzlechamber. In addition, the entire roof is covered with a layer ofpolydimethylsiloxane (PDMS). The PDMS layer 126 has a multitude offunctions, including: protection of the bend actuator, hydrophobizingthe roof 104 and providing a mechanical seal for the gap 109. The PDMSlayer 126 has a sufficiently low Young's modulus to allow actuation andejection of ink through the nozzle opening 112.

A more detailed description of the PDMS layer 126, including itsfunctions and fabrication, can be found in, for example, U.S.application Ser. No. 11/946,840 filed on Nov. 29, 2007 (the contents ofwhich are herein incorporated by reference).

When it is required to eject a droplet of ink from the nozzle chamber122, a current flows through the active beam 114 between the electrodecontacts 118. The active beam 114 is rapidly heated by the current andexpands relative to the passive beam 116, thereby causing the movingportion 108 to bend downwards towards the substrate 102 relative to thestationary portion 110. This movement, in turn, causes ejection of inkfrom the nozzle opening 112 by a rapid increase of pressure inside thenozzle chamber 122. When current stops flowing, the moving portion 108is allowed to return to its quiescent position, shown in FIGS. 2 and 3,which sucks ink from the inlet 124 into the nozzle chamber 122, inreadiness for the next ejection.

From the foregoing, it will be appreciated that the PDMS layer 126significantly improves operation of the nozzle assembly 100. Asdescribed in U.S. application Ser. No. 11/946,840, the formation of thePDMS layer 126 is made possible through the integration of spin-onphotopatternable PDMS with a MEMS fabrication process. The Applicant hasdeveloped a versatile MEMS fabrication process utilizingphotopatternable PDMS, which may be modified for use in a plethora ofapplications. Microfluidics devices and systems utilizing PDMS aredescribed hereinbelow.

Microfluidic Pump

FIGS. 4 and 5 show a linear peristaltic pump 200, comprising a row ofMEMS devices, each of which is similar in construction to the thermalbend-actuated inkjet nozzle assembly 100 described above. FIG. 4 showsthe pump 200 in perspective view with an upper PDMS layer removed toreveal details of each MEMS device.

The linear peristaltic pump 200 is formed on a surface of a CMOS siliconsubstrate 202. A pumping chamber 203 is defined by a roof 204 spacedapart from the substrate 202 and sidewalls 206 extending from the roofto the substrate 202. The roof 204 and sidewalls 206 are typicallycomprised of silicon oxide or silicon nitride and are constructed usinga fabrication process analogous to the process described in U.S.application Ser. No. 11/763,440.

The pumping chamber 203 takes the form of an elongate channel extendinglongitudinally between a pump inlet 208 and a pump outlet 210. As shownin FIG. 4, the pump inlet 208 is defined in a floor 212 of the pumpingchamber 203 and a fluid is fed to the pump inlet 108 via a pump inletchannel 214 defined through the silicon substrate. The pump outlet 210is defined in the roof 204 of the pumping chamber 203, at an oppositeend to the pump inlet 108. This arrangement of pump inlet 208 and pumpoutlet 210 is specifically configured for providing fully integrated LOCdevices as described below. However, it will be appreciated that in itsbroadest form, the peristaltic pump 200 may have any suitablearrangement of pump inlet and outlet, provided that peristaltic pumpingfingers are positioned therebetween.

FIG. 4, having the upper PDMS layer removed, shows three peristalticpumping fingers 220 arranged in a row and spaced apart along thelongitudinal extent of the pumping chamber 203. By analogy with theinkjet nozzle assembly 100 described above, each finger 220 is moveableinto the pumping chamber 203 by thermal bend actuation. Thus, eachfinger 220 comprises a MEMS thermal bend actuator in the form of anactive beam 222 cooperating with a passive beam 224. Typically, theactive beam 222 is fused to the passive beam 224, and the passive beam224 defines the extent of each moving finger 220.

The passive beam 224 is usually formed of the same material as the roof204, and the finger 220 is separated from the roof by a perimeter gap226, which is defined by an etch process during MEMS fabrication.

The active beam 222 defines a bent current path extending between a pairof electrode contacts 228. In keeping with the inkjet nozzle assembly100, the active beam 222 comprises a pair of arms 229 extending fromrespective electrode contacts 228. The arms 229 are connected at theirdistal ends by a connecting member 230.

Each finger 220 extends transversely across the roof 204 of thelongitudinal channel defined by the pumping chamber 203. Hence, it willbe appreciated that by controlling movement of each finger 220, aperistaltic pumping action may be imparted on a fluid contained in thepumping chamber 203. The skilled person will be aware of linearperistaltic pumps employing a similar pumping action, as described in,for example, U.S. Pat. No. 4,909,710, the contents of which are hereinincorporated by reference.

Control of each finger actuation is provided by a CMOS layer 240 in thesilicon substrate 202, shown in FIG. 5. FIG. 5 is a perspective of thepump 200 including an upper polymeric sealing layer 242 of PDMS. Thepump 200 is cutaway through one of the fingers 220 to reveal part of ametal CMOS layer 240. The CMOS layer 240 connects with each electrodecontact 228 via a connector post 244, which extends from the CMOS layer,through the sidewalls 206, and meets with the electrode contact. TheCMOS layer 240 contains all the necessary control and drive circuitryfor actuating each finger 220. Hence, a chip comprising the pump 200contains all the requisite control and drive circuitry for actuating thepump, without the need for any external off-chip control. On-chipcontrol is one of the advantages of the pump 200 according to thepresent invention.

Moreover, in contrast with peristaltic pumps built from an array of‘Quake’ valves (as described in U.S. Pat. No. 7,258,774), the pump 200does not require any control fluid (e.g. air) to drive the peristalticaction. Whereas ‘Quake’ valves (and thereby ‘Quake’ pumps) are relianton fluid in a control channel, which must be supplied externally, themechanically-actuated pump 200 is fully self-contained and does notrequire any external input, except, of course, for the actual fluidwhich is to be pumped.

Referring again to FIG. 5, the polymeric sealing layer 242 (typicallyPDMS) is deposited onto the roof 204, and the pump outlet 210 definedtherethrough, using fabrication techniques analogous to those describedin U.S. application Ser. No. 11/763,440. Of course, the polymeric layer242 has sufficiently low Young's modulus to enable movement of eachfinger 220 during actuation. The polymeric layer 242 principallyprovides a mechanical seal for the perimeter gap 226 around each finger220, but also provides a protective layer for each thermal bendactuator.

Furthermore, PDMS provides an ideal bonding surface for bonding a MEMSintegrated circuit comprising the microfluidic pump 200 to aconventional microfluidics platform formed by soft lithography.Integration of a MEMS integrated circuit with a conventional LOCplatform is a particularly advantageous feature of the present inventionand will be described in more detail below.

Alternative Microfluidic Pump

Of course, the pump 200 may take many different forms. For example, thenumber and orientation of the fingers 220 may be modified to optimizethe peristaltic pumping action. Turning now to FIG. 6, there is shown inplan view an alternative linear peristaltic pump 250 employing the sameoperational principles as the pump 200 described above. In FIG. 6, theupper polymeric layer 242 has been removed to reveal the individualfingers 220 and the pumping chamber 203. In the interests of clarity,like reference numerals have been used to describe like features in FIG.6.

Thus, the pump 250 comprises a pumping chamber 203 in the form of alongitudinal channel. Pairs of opposed fingers 220 are positioned in theroof of the chamber 203, and a plurality of finger pairs extendlongitudinally in row along the chamber. Each finger 220 in a pairpoints towards a central longitudinal axis of the chamber 203 so as tomaximize the peristaltic pumping action by simultaneous actuation ofboth fingers in a pair. During pumping, opposed pairs of fingers may beactuated (e.g. sequentially) to provide the peristaltic pumping action.Of course, any sequence of actuations may be employed to optimizepumping, as described in, for example, U.S. Pat. No. 4,909,710. In somepumping cycles, more than one finger pair may be actuatedsimultaneously, or some finger pairs may be partially actuated. Theskilled person will readily be able to conceive of optimal peristalticpumping cycles, within the ambit of the present invention, utilizing thepump 250.

Still referring to FIG. 6, the fingers 220 are positioned between a pumpinlet 208 and a pump outlet 210. An outlet channel 252 between the pumpoutlet 210 and the fingers 220 comprises a valve system 254. The valvesystem 254 comprises a channel circuit 256, which is configured tominimize backflow of fluid from the outlet 210 towards the inlet 208.Thus, the valve system 254 further optimizes the efficiency of the pump250. Although a very simple valve system 254 is shown in FIG. 6, it willappreciated that any check valve may be used to improve the efficiencyof a one-way pump according to the present invention.

Of course, pumps according to the present invention may be madereversible, simply by altering the sequence of finger actuations via theon-chip CMOS.

Fully Integrated LOC Device Comprising MEMS Micropumps

As foreshadowed above, a PDMS polymeric layer 242 provides an idealbonding surface for bonding MEMS integrated circuits to conventionalmicrofluidic platforms formed by soft lithography. This enablesintegration of CMOS control circuitry with microfluidic devices in afully integrated LOC device. Therefore, a significant advantage isachieved by obviating the need for external off-chip control systems andpumping systems, which are usually required in conventional LOC devices.

Interfacial bonding between a conventional PDMS microfluidics platformand a PDMS-coated MEMS integrated circuit is achieved using conventionaltechniques known from multilayer PDMS soft lithography. Such techniqueswill be well known to a person skilled person in the art of softlithography. Typically, each PDMS surface is exposed to an oxygen plasmaand the two surfaces bonded together by applying pressure.

FIG. 7 shows how a simple integrated LOC device according to the presentinvention may be fabricated using a conventional PDMS bonding technique.A MEMS integrated circuit (or chip) 290 comprises a silicon substrate202, a CMOS layer 240 and MEMS layer 260. The MEMS layer 260 comprisesMEMS microfluidic pumps 200. In the schematic integrated circuit 290,two MEMS microfluidic pumps 200A and 200B are shown, each comprising aplurality of thermal bend-actuated fingers 220 for providing aperistaltic pumping action. Of course, in practice, each MEMS integratedcircuit 290 may comprise many hundreds or thousands of MEMS devices,including the pumps 200.

The MEMS layer 260 is covered with the PDMS layer 242, which defines anexternal bonding surface 243 of the integrated circuit 290.

A conventional microfluidics platform 295 is comprises of a body 280 ofPDMS in which is defined a plurality of microfluidic channels, chambersand/or microfluidic devices. In the schematic microfluidics platform 295shown in FIG. 7, there is shown a ‘Quake’ valve 282 comprising a fluidicchannel 284 cooperating with a control channel 286. An arbitraryreaction chamber 288 is also defined in the PMDS body 280. It will beappreciated that any three-dimensional microfluidics platform 295 may beformed by conventional soft lithographic techniques, as known in theart.

The body 280 of the microfluidics platform 295 has a bonding surface281, in which is defined a control fluid inlet 283 and a fluid channelinlet 285. The control fluid inlet 283 and fluid channel inlet 285 arein fluid communication with their respective control channel 286 andfluid channel 284. The control fluid inlet 283 and fluid channel inlet285 of the microfluidics platform 295 are positioned to align with pumpoutlets 274 and 276 defined in the PDMS layer 242 of the MEMS integratedcircuit 290.

The two bonding surfaces 243 and 281 are bonded together by exposingeach surface to an oxygen plasma and then applying pressure. Theresultant bonded assembly, in the form of an integrated LOC device 300,is shown in FIG. 8.

In the integrated LOC device 300, the pumps 200 controlled by the CMOSlayer 240 of the integrated circuit 290 pump fluid into microfluidicchannels 286 and 284 of the PDMS microfluidics platform. The pumps 200may pump either control fluid (for driving valves in the PDMS platform295) or actual sample fluids used by the device (e.g. fluids foranalysis). Accordingly, the CMOS control circuitry can be used toprovide full control over operation of the integrated LOC device 300.

A simple example will now be described to illustrate how the LOC device300 may be operated in practice. A control fluid enters a first inlet270 and is pumped, using the microfluidic pump 200A, into the controlchannel 286 of the microfluidics platform 286. The control channel 286becomes pressurized with the control fluid. As described above inconnection with FIGS. 1A-C, the control channel 286 overlays andcooperates with part of the fluid channel 284 to form the valve 282.When the control channel 286 is pressurized with the control fluid, awall of the fluid channel 284 is collapsed, which closes the valve 282.Accordingly, a section of the fluid channel 284 downstream of thechamber 288 is closed by the valve 282, thereby fluidically isolating adevice outlet 287 from the chamber 288.

With the valve 282 closed, a sample fluid entering a second inlet 272 ispumped, using microfluidic pump 200B, into the chamber 288 via the fluidchannel 284. Further fluids (e.g. reagents) may be also be pumped intothe chamber 288 via further fluid channels (not shown). Once all fluidshave been pumped into the chamber 288 and sufficient time has elapsed,the valve 282 may be opened by shutting off the pump 200A, and allowingfluid to flow through the downstream section of the fluid channel 284towards the device outlet 287.

This simple example illustrates how the integrated LOC device 300 canprovide full control over LOC operations via the CMOS circuitry and MEMSmicropumps 200. It is a particular advantage of the LOC device 300 thatexternal, off-chip pumps and/or control systems are not required. Thecontrol fluid may be either air (providing pneumatic control of thevalve 282) or a liquid (providing hydraulic control of the valve 282).

Although the example provided herein is very simple, the skilled personwill appreciate that the present invention may be used to providecontrol of a complex LOC device having a complex, labyrinthine array ofvalves, pumps and channels.

A notable advantage of the present invention is that it fullycomplements existing LOC technology based on soft lithographicfabrication of microfluidics platforms. Complex microfluidics platformshave already been fabricated using soft lithography. These conventionalplatforms would require only minor modifications in order to beintegrated into the CMOS-controllable LOC devices provided by thepresent invention.

Microfluidic Valves

As foreshadowed above, silicon-based MEMS technology has inherentlimitations in the microfluidics and LOC fields. Microfluidic valves areusually essential in LOC devices and hard, inflexible materials such assilicon are unable to provide the sealing engagement required in avalve. Indeed, this limitation was the primary reason that microfluidicsmoved away from silicon-based MEMS lithography into soft lithography,based on compliant polymers, such as PDMS.

Hitherto, the present Applicant has demonstrated how PDMS can beintegrated into a conventional silicon-based MEMS fabrication process.It will be described how this same technology enables effectivemicrofluidic valves to be created using conventional silicon-based MEMStechnology. Moreover, such valves do not require external fluidicsupplies or control systems, in contrast with the ‘Quake’ valvesdescribed above. Two types of valve are described below, although theskilled person will be able to conceive of many other variants byintegrating PDMS into a silicon-based MEMS fabrication process. In eachcase, engagement of a PDMS surface with another surface (e.g. siliconsurface, silicon oxide surface, PDMS surface etc.) provides the sealingengagement necessary for a valving action. Furthermore, each valve takesthe form of a mechanically-actuated valve, where engagement of opposedsurfaces is driven by actuation or deactuation of a thermal bendactuator, which is itself controlled by on-chip CMOS.

Valve Providing Closure in a Polymeric Microfluidics Channel

Referring to FIG. 9, there is shown a microfluidics pinch valve 310resulting from bonding of a polymeric microfluidics platform 312 and aMEMS integrated circuit 314 having a surface layer of PDMS 316. The PDMSlayer 316 defines a first bonding surface 313 of the MEMS integratedcircuit 314.

The MEMS integrated circuit 314 comprises an actuation finger 318constructed on a CMOS silicon substrate 315. The actuation finger 318may be identical in design to one of the fingers 220 described above inconnection with FIGS. 4 and 5. Thus, although the actuator finger 318 isshown only schematically in FIG. 9, it can be assumed that it containsall features, including the thermal bend actuator, described above inrelation to the fingers 220.

The microfluidics platform 312 is formed by standard soft lithographyand comprises a polymeric body (e.g. PDMS body) 320, in which is defineda microfluidics channel 322. The channel 322 includes a sleeve portion324, which passes adjacent a second bonding surface 325 of themicrofluidics platform 312. The sleeve portion 324 is separated from thesecond bonding surface 325 by a layer of PDMS which defines an exteriorwall 326 of the sleeve portion. The exterior wall 326 comprises acompression member 328, which protrudes from the exterior wall andextends away from the second bonding surface 325.

As can be seen from FIG. 9, when the two bonding surfaces 313 and 325are bonded together, the compression member 328 is aligned with theactuation finger 318. By virtue of projecting from the exterior wall326, the compressions member 328 abuts against the first bonding surface313 during the bonding process, and is consequently compressed againstan interior wall 330 of the sleeve portion 324. Hence, the sleeveportion 324 is pinched closed by the bonding process.

In the assembled LOC device 350 shown in FIG. 9, the valve 310 is closedwhen the actuation finger 318 is in its quiescent state, and no fluidcan pass through the sleeve portion 324. Referring now to FIG. 10, thefinger actuator 318 is actuated and bends downwards, thereby pulling thecompression member 318 with it towards the silicon substrate 315. Thisactuation urges the exterior wall 326 away from the interior wall 330and, hence, the valve 310 is opened so as to allow fluid to pass throughthe sleeve portion 324.

It is an advantage of the valve 310 that it is biased to be closed whenthe finger actuator 318 is in its quiescent state. This means that a LOCdevice comprising the valve 310 will not be power hungry. A furtheradvantage is that it is possible to regulate opening of the valve bymodulating an actuation power supplied to the finger actuator 318.Partial valve closures may be readily achieved using thismechanically-actuated pinch valve.

Self-evidently, a plurality of valves 310 may be arranged in series toprovide a microfluidic device 340, as shown in FIG. 11. The device 340may be configured to provide a peristaltic pumping action.

Alternatively, the device 340 may simply provide a more effectivevalving action via concerted actuation of each finger actuator 318.

The device 340 can also be configured to create a turbulent flow, whichis useful for mixing fluids. Typically, fluids flowing on a microscaleare difficult to mix due to laminar flow. Accordingly, the device 340may be used as a “micromixer”. It will be appreciated that optimalmixing actions may be different from peristaltic pumping actions. It isadvantage of the present invention that the device 340 may be usedinterchangeably as either a valve, a micromixer or peristaltic pump. TheCMOS control circuitry may be configured to provide either a valvingaction, a mixing action or a pumping action in the device 340, simply byaltering an actuation sequence for the finger actuators 318.

Alternatively, when used as a pump, the device 340 may be ‘tuned’ to theindividual characteristics of a particular fluid. For example, moreviscous liquids may require a different (e.g. slower) peristalticpumping cycle to less viscous liquids. It is an advantage of the presentinvention that the CMOS control circuitry, individually controlling eachfinger actuator 318, may be configured accordingly so as to ‘tune’ thepump to the characteristics of particular fluid. The control achievableby the on-chip CMOS circuitry would not be possible using traditionalLOC technology.

Valve Providing Closure in a Silicon Microfluidics Channel

Referring to FIGS. 12 and 13, there is shown a microfluidicsdiaphragm-type valve 350 formed on a CMOS silicon substrate 351. Thevalve 350 is entirely self-contained in a MEMS integrated circuit 360.Thus, the valve 350 potentially obviates the need for bonding the MEMSintegrated circuit 360 to a microfluidics platform altogether, since theMEMS integrated circuit can contain all the control circuitry,microchannels, valves and pumps required to create a complete LOC deviceor μTAS. The valve 350 paves the way for LOC devices constructedentirely using silicon-based MEMS technology, as opposed to softlithography, which has now become standard in the art.

Alternatively, the MEMS integrated circuit 360 may still be bonded to amicrofluidics platform, as described above. It will be appreciated thatmicrochannels in a microfluidics platform may be connected to fluidoutlets (not shown) in the MEMS integrated circuit 360 to create a LOCdevice.

Turning now to FIGS. 12 and 13, the valve 350 comprises a pair ofopposed first and second actuation fingers 352 and 353, which both pointtowards a central saddle or weir 354 having a sealing face 355. The weir354 is essentially a block of silicon oxide, which may be defined at thesame time as sidewalls 357 of the valve 350 are defined during MEMSfabrication. It will be appreciated that each finger 352 and 353 issimilar in design to the fingers 220 described above.

The weir 354 divides the valve 350 into an inlet port 356 and an outletport 358. A layer of PDMS 359 bridges between the first and secondactuation fingers 352 and 353 to form a roof 362, which acts as adiaphragm membrane for the valve 350.

As shown in FIG. 12, the inlet port 356 fluidically communicates withthe outlet port 358 via a connecting channel 361, which is definedbetween the sealing face 355 of the weir 354 and the roof 362. In FIG.13, each of the fingers 352 and 353 is actuated and bends downwardstowards the silicon substrate 351. This bending of the fingers 352 and353, in turn, pulls the roof 362 into sealing engagement with thesealing face 355 of the weir 354. This sealing engagement between theroof 362 and the sealing face 355 prevents any fluid flowing from theinlet port 356 to the outlet port 358 (and vice versa). Hence, the valve350 is closed as shown in FIG. 13.

Subsequent deactuation of the fingers 352 and 353 releases the roof 362from sealing engagement with the sealing face 355 as the fingers returnto their quiescent state shown in FIG. 12.

Hence, a highly effective diaphragm valve 350 is provided, which makesuse of a PDMS covering to provide a sealing diaphragm membrane for thevalve. By using PDMS in this way, an effective valve can be made formicrofluidic channels defined in rigid materials, such as asilicon-based MEMS integrated circuit. It will be appreciated that sucha valve may be used in a variety of microfluidic systems, such as LOCdevices.

It will, of course, be appreciated that the present invention has beendescribed purely by way of example and that modifications of detail maybe made within the scope of the invention, which is defined by theaccompanying claims.

1. A mechanically-actuated microfluidic valve comprising: an inlet port; an outlet port; a thermal bend actuator; and a valve closure member cooperating with said actuator, such that actuation of said thermal bend actuator causes movement of said closure member, thereby regulating a flow of fluid from said inlet port to said outlet port.
 2. The microfluidic valve of claim 1, wherein said thermal bend actuator comprises: an active beam comprised of a thermoelastic material; and a passive beam mechanically cooperating with said active beam, such that when a current is passed through the active beam, the active beam heats and expands relative to the passive beam, resulting in bending of the actuator.
 3. The microfluidic valve of claim 2, wherein said active beam is fused to said passive beam.
 4. The microfluidic valve of claim 2, wherein said active beam defines a bent current path extending between a pair of electrodes, said electrodes being connected to control circuitry for controlling said actuator.
 5. The microfluidic valve of claim 2, wherein said thermoelastic material is selected from the group comprising: titanium nitride, titanium aluminium nitride and vanadium-aluminium alloys.
 6. The microfluidic valve of claim 2, wherein said passive beam is comprised of a material selected from the group comprising: silicon oxide, silicon nitride and silicon oxynitride.
 7. The microfluidic valve of claim 1, wherein at least said actuator is defined in a MEMS layer of a silicon substrate.
 8. The microfluidic valve of claim 7, wherein said substrate comprises control circuitry for controlling said actuator, said control circuitry being contained in at least one CMOS layer of said substrate.
 9. The microfluidic valve of claim 1, wherein said inlet port and said outlet port are defined in a MEMS layer of a silicon substrate.
 10. The microfluidic valve of claim 1, wherein said inlet port and said outlet port are defined in polymeric microfluidics platform.
 11. The microfluidic valve of claim 1, wherein said closure member is comprised of a compliant material for sealing engagement with a sealing surface of said valve.
 12. The microfluidic valve of claim 1, wherein said closure member is comprised of an elastomer.
 13. The microfluidic valve of claim 1, wherein said closure member is comprised of polydimethylsiloxane (PDMS).
 14. The microfluidic valve of claim 1, wherein said closure member is fused or bonded to said thermal bend actuator.
 15. The microfluidic valve of claim 1, wherein said actuation causes open or closing of said valve.
 16. The microfluidic valve of claim 1, wherein said actuation causes partial opening or partial closing of said valve. 